Hangovers are a combination of dehydration and dropping alcohol levels in the brain. The first has the obvious answer. A long watery non-alcoholic drink between alcoholic ones may prevent it, but if you are drinking too much it won't stop the second. Even if you are well hydrated, high alcohol levels in the blood and brain poison you - hence the nausea (an irritated stomach and toxic liver) and headache (a swollen brain). You only lose about 10% of your blood alcohol level per hour, so you may well be over the limit for driving next day, even without a hangover. It's best to drink plenty of water with electrolytes in it - such as the sachets you can get for diarrhoea - and give your stomach a rest for 24 to 36 hours.

I get mouth ulcers several times a year. Why is this, and what can I do to stop this cycle? A friend says she used dabs of methylated spirit on hers.

The answer is - I don't know. Amazingly, for such a common condition, researchers haven't yet found the cause of mouth ulcers. There may be viruses involved, but they certainly aren't related to, say, cold sores, about which we do know a lot. As for preventing future attacks, we aren't sure about that either. Keeping your teeth and gums scrupulously clean and healthy may help. That means regular visits to your dentist and dental hygienist, and stopping smoking. As for meths - wow! It's a poison, and not to be put in your mouth at any time. Stick to cortisone tablets placed on ulcers to ease the pain.